Furcation development of human mandibular first molar teeth. A histologic graphic reconstructional study.

Abstract

A study was performed to clarify the temporal sequence of bifurcation development in human mandibular first molar teeth and to investigate the development of features of bifurcation morphology previously described in extracted teeth. This report presents the histometric findings from graphically reconstructed teeth at varying stages of development.Sixteen developing teeth were graphically reconstructed from tracings of serial sections of thirteen grossly and histologically normal human foetuses ranging in post fertilization age from 17 to 38 weeks. Accuracy of reconstruction was tested by retracing and repeated reconstruction and found to be acceptable.Furcation development began at about 24 weeks post fertilization with the appearance of two epithelial nodes which approximately maintained their position relative to one another at a time when the rest of the developing tooth expanded. These nodes were joined to the epithelial cap by isthmuses of epithelial cells. As furcation development occurs prior to root formation, it should be considered part of crown development. In the area of the developing furcation entrance the buccal isthmus of epithelial cells was narrower mesio‐distally than the lingual isthmus. The epithelial nodes and associated isthmuses were located within the ectomesenchymal tissue of the base of the dental papilla.These findings suggest the embryologic origins of enamel projections into the furcation, the difference in diameter between the buccal and lingual furcation entrances, and the abundance of cementum in the furcation area.An incomplete epithelial diaphragm, such as has been described in the marmoset, was not observed in any of the specimens examined.